/Engine/Source/Editor/UnrealEd/Public/FileHelpers.h
Helper function used to decide whether a package name is a map package or not. Map packages aren't added to the additional package list.
True if package is a map
static bool IsMapPackageAsset ( const [FString](API\Runtime\Core\Containers\FString) & ObjectPath, [FString](API\Runtime\Core\Containers\FString) & MapFilePath )